Sensor arrangements that comprise magnetic field sensors for measuring magnetic field intensity can be used to determine an angular deviation of a magnetic source in relation to the position or orientation of the magnetic field. Diametrically magnetized and rotatably seated magnetic sources are frequently used for this.
The magnetic field sensors can be arranged along a circular periphery and provide sensor signals over this periphery that form approximately a sinusoidal curve, depending on the position and orientation of the magnetic source. For a diametrically magnetized magnet, for example, sensor signals from magnetic field sensors can be evaluated in such a manner that an angle of rotation of the magnetic source can be determined within a full rotation of 360° based on the measured signals.
Examples of methods and arrangements for determining an angle of rotation are disclosed, for instance, in the publication EP 1967824 A1, which is hereby incorporated by reference in the full scope of its disclosure.
For a precise angle determination, however, it is advantageous if an axis of rotation of the magnet runs through the center of the circularly arranged magnetic field sensors. In this case a uniform sinusoidal curve over all the magnetic field sensors along the circular periphery appears, without the occurrence of variations of the respective signal amplitudes as a function of the angle of rotation.
In the construction of a measurement arrangement, it is possible for a reference point to be marked in a housing of an integrated module, for example, with which the axis of rotation of the magnetic source can be oriented optically or mechanically. However, if the arrangement is mounted in the interior of the housing that comprises the magnetic field sensors, with a specified tolerance of its position in the housing, there can nevertheless be deviations between the axis of rotation and the center of the magnetic field sensors, so that measurement precision is impaired.
Alternatively, a curve of measured magnetic field intensities can be evaluated over a full revolution of the magnet by means of a linearity observation in order to find an optimal position for the axis of rotation of the magnetic source. Such a method is connected with an increased effort in terms of time and production technology, however.